Recent years have seen active development of a display technology called a see-through display (transparent display) which not only displays an image on a screen but also allows an object behind the display to be viewed through the screen. To realize see-through displays, there have been proposed various approaches such as approaches using liquid crystal panels and organic EL (electroluminescent) panels.
For example, International Publication WO 2014/010585 describes a display including a translucent light guiding plate (self-luminous means) as well as a transparent display and a transparent plate, which are disposed opposite the light guiding plate on the front side. Light emitted by the light guiding plate is transmitted through the transparent display to the eye of the user. Accordingly, even if natural light is insufficient, the visibility of displayed content does not decrease.
Moreover, Japanese Laid-Open Patent Publication No. 2007-148442 describes a display including a translucent light guiding plate (self-luminous means), a transparent display, absorptive polarizing plates, and a reflective polarizer, in which the transparent display and the absorptive polarizing plates are disposed opposite the light guiding plate on the front side, and the reflective polarizer is disposed opposite the light guiding plate on the hack side. Light emitted by the light guiding plate is either directly transmitted through the transparent display, or reflected by the reflective polarizer before the transmission through the transparent display, and reaches the eye of the user. This enhances light usage efficiency and thereby enhances the visibility of displayed content.